Process of dyeing modified polyacrylonitrile staple fabric



Patented Feb. 19, 1%53 UNITE PR-QCESS F DYEING MODIFIED POLY-ACRYLUNETRILE STAPLE FABRIC 1 Louis Meunier, Wilmington, .DeLyand .Wjl-

am Wygand, .irn, Perms .Grove, N. .L, assignors to E. I. du Pont deNemours '& Company, -Wilmington, Eel, a corporation of Delaware NoDrawing. Application s eptem'ber'i); 1-950, Serial No. 184,106

Claims. 1

This invention relate to a process of dyeing modified polyacrylonitrilestaple fabric in rope form. It is an object of this invention to improvethe process of dyeing fabric of the aforcsaid nature with acid colors.important objects of this invention will the description proceeds.

Modified polyacrylonitrilc material as used herein refers to copolymersof acrylonitrile and vinyl pyridines or vinyl picolines, as disclosed inArnold, U. S. P. 2,491,471. Modified polyacrylonitrile staple fabric isfabric woven or knitted groin yarns spun from staple fibers of modifiedpolyacrylonitrile material. Such fabric generally dyed in rope form. Inthis system of dyeing, one or more bolts of fabric arerun side oy' sideover thereel of a heck machine, the two ends of each bolt of fabricbeing sewn together to form a continuous band of fabric. As the fabricfalls off the reel into the heck it forms folded pile in the beck, andthe reel rotates, each portion of the band of fabric is continuouslydipped in and drawn out of the dye bath. A handy description or" thismethod, with sketches of the apparatus, occurs in the American WoolHandbook, 2nd ed. (1948), at pages 748-751.

Modified polyacrylcnitril-o material is specially suited for dyeing withacid dyestuffs, whereas unmodified acrylonitrile polymers have noailinity for this type of dye. In the case of staple fabric, however,when dyed in rope form, the longitudinal creases formed by the roping ofthe fabric band on the reel as well as the horizontal folds formed inthe beck interfere with the production of level dyeings. Uneven dyestreaks appear in the fabric, probably due to improper penetration ofthe dye bath at the creases and folds.

We have now found that the above detect c..n be corrected if the dyeingis effected in the presence of a small quantity of a phenyl-carboxylicacid, such as benzoic acid or salicylic acid. By small quantity. we meana concentration of 0.5 to 2% (i. e. 5 gm./l. to 20 gm./l.). Furthermore,we find that dyeing can be achieved at a somewhat lower temperature(180-200 F.) then in the absence of the mentioned auxiliary agents whichrequires 205-212 F.)

Apart from the above detail, the dyeing may proceed along conventionallines, or may follow the special details devised in the art forpolyacrylonitrile or modified polyacrylonitrile material. Thus, the dyemay be any desirable acid dye which is applicable to modifiedpolyacrylonitrile material. Its concentration in the dye bath may varywithin wide limits depending on the strength of shade Jclesired..Sulfufic :acid in quantity usually not exceeding 0.1 part .for eachpart by weight of fabric being dyed, may be added as dyeing proceeds, toassist inexhausting the dye bath.

Without limiting our invention, the Iollowing examples are given :toillustrate our preferred mode of procedure. Parts mentioned are byweight. .C. .1. numbers refer to the well known Colour Index numbers.Pr. numbers are the Prototype numbers assigned to colors in the Yearbookof A. A. T. C. C..for 1%9.

Example 1 One part of staple "fabric woven of modified polyacrylonitrile.fibcr was dyed in rope form in a heck in 6.0 parts of liquor containing0.3 part (5 g./1.) of salicylic acid and 0.01 part the red dye listed as#430 :in the Colour Index. After dyeing .for 30 .minutes at 200 F., 0.09part of sulfuric acid was added and the dyeing was continued for anadditional 30 minutes at 200 F. A level and well penetrated dyeing wasobtained.

Example 2 A staple fabric of modified polyacrylonitrile fabric was dyedfor one hour'at 200 F. with 0.01 part of the red dye referred to inExample 1, using 20 grams per liter of salicylic acid. In this case nosulfuric acid was added. A bright, level and completely penetrateddyeing was obtahied.

Example .5

A thirty-two yard length of staple fabric of modified polyacrylonitrile.weighing fifteen pounds, was worked for minutes at 170 F. in 250 gallonsof a bath containing 5.0,g./l. of salicylic acid. 118 grams of the navyblue dye. C. I. #304 and 43.5 grains of the blue dye, Pr. #12,previously dissolved in Water, were then added. The temperature of thebath was raised to 200 F., during one hour, and dyeing was continued atthis temperatureior 1 /2 hours, during: which period 2 pints of sulfuricacid were added in small portions. The bath was then flooded and thefabric was secured for minu as at 200 in 250 gallons of water, to whichhad been added grains of the .sodidm salt of oleylmethyl taurine (asynthetic detergent) and 1 quart of concentrated ammonium hydroxide. Thefabric was then rinsed thoroughly and dried. It exhibited goodlevelness, being substantia .y free from rope creases.

Example 4 Thirty-two yards of staple fabric made of modifiedpolyacrylonitrile and weighing fifteen pounds was treated in rope formon a heck in 200 gallons of water to which 8 lbs. of salicylic acid hadbeen added. After the goods had been worked in this bath for 30 minutesat 170 F., 71 grams of the brown dye described in Example 1 of U. S.2,093,356 and 18 grams of 4,4'-diamino- 1,1'-dianthrimide disulfonicacid disodium salt (a gray dye), were added. The temperature was raisedto 180 F., and dyeing was continued at this temperature for one hour.One pine of sulfuric acid was added over a period of 30 minutes, duringwhich the temperature was raised to 200 F., and dyeing was continued atthis temperature for one hour longer. The bath was then flooded and thefabric was washed for 20 minutes at 200 F. In 200 gallons of watercontaining 50 grams of the synthetic detergent mentioned in Example 3,and 1 quart of concentrated ammonium hydroxide. The goods were thenrinsed thoroughly and dried. A level, well penetrated dyeing wasobtained.

Example 5 One piece of a modified polyacrylonitrile fabric weighing 9.4kg. was entered into 100 gallons of water containing 1.9 kg. ofsalicylic acid (5 g./l.) at a temperature of 180 F., and worked thereinfor 20 minutes. To this bath, 365 grams of the brown dyestufi, C. I.#105, and 94 grams of the yellow dyestuif, C. I. #40, were addedportionwise over a period of 20 minutes. The bath was raised to atemperature of 200 F. over a period of 20 minutes, and the goods wereworked therein at 200 F. for 45 minutes. Dyeing was then continued atthe same temperature for two hours longer, during which period 300 cc.of concentrated sulfuric acid were added in three portions. The goodswere then washed well and subjected to chroming in a fresh bath of 200gallons of water containing 200 grams of sodium dichromate and 200 cc.of concentrated sulfuric acid. This operation was carried out for onehour at 205 F.. and for one hour longer at 210 F. The goods were thenwashed thoroughly, hydro-extracted,

and dried on a tenter. A level, dark brown dyeing was obtained.

Example 6 A fabric of modified polyacrylonitrile staple fabric was dyedon a beck in a dye bath containing a combination of dyestuffs asfollows:

3% (on weight of fabric) sodium salt ofbenzeneazo-beta-naphthol-G:8-disulfonic acid (0. I.

Salicylic acid in quantity of five grams per liter was added to the dyebath, and the fabric was dyed for thirty minutes at 200 F. An additionof 6 per cent sulfuric acid (on weight of fabric) was made and dyeingcontinued for 30 minutes at 200 F. A level, well penetrated dyeing wasobtained.

It will be understood that the details of the above examples may bevaried within the skill of those engaged in this art. Thus, the ratio ofdye bath to fiber may be several fold the ratios used in the aboveexamples, provided the concen- 4 tration of salicylic acid is keptwithin the limits indicated (i. e. 5 to 20 g./l.).

Instead of adding salicylic acid directly to the bath, the fabric may bepretreated with a salicylic acid bath of the indicated concentrationrange prior to dyeing.

For best light fastness results, it is recommended that the dyed fabricbe secured with soap and alkali, such as NHQOH, to remove excess acid.

In lieu of salicylic acid, benzoic acid may be employed. Homologs andhalogen derivatives of these acids are also useful. In general, theauxiliary agents recommended by this invention may be defined by theformula wherein X and Y each stand for hydrogen, methyl, hydroxy orchlorine. The preferred auxiliary agents are those which are soluble inwater to the extent of at least 5 grams per liter at temperatures of 180to 200 F. However, this is not an absolute condition, inasmuch asdispersing agents may be employed where the auxiliary agent selecteddoes not possess sufiicient solubility.

Chrome dyes are merely a branch of the acid dye family, differing fromthe other members only in the fact that they require an afterchromingtreatment. In agreement with this general proposition, we find that ourinvention may be practiced to advantage also with chrome dyes, theprocedure being essentially the same as in the aforegoing examples,except that the dyed fabric is given an after-chroming treatment withsodium or potassium dichromate and sulfuric acid.

Furthermore, although direct colors are not generally classed as aciddyes, they seem to behave like acid dyes when applied to modifiedpolyacrylonitrile fiber. In any event, we find that our invention,substantially as outlined in the above examples (including exhaustion ofthe bath by the aid of sulfuric acid), may be applied to advantage inthe case of many colors which are normally classified as direct colors.

As additional illustrations of dyes coming within the above classes andactually tested by us with good results, the following may be mentioned:

Chrysophenine, C. I. 365

Diamine Fast Red F, C. I. 419 Benzo Fast Red 8BL, C. I. 278 Benzo FastHeliotrope, C. I. 319 Polar Yellow, C. I. 642

Brilliant Crocein M, C. I. 252 Alizarin Supra Blue A, Pr. l2 AlizarinSky Blue B, C. I. 1088 Alizarin Cyanine Green, C. I. 1078 Polar Red, C.I. 430

Fast Red A, C. I. 176

Acid Anthracine Brown R, C. I. 105 Alizarin Yellow R. C. I. 40

Alizarin Yellow 2G, C. I. 36 Eriochrome Black T, C. I. 203

We are aware of Richards, U. S. P. 2,512,969, wherein it is recommendedto dye polyacrylonitrile with acetate and basic dyes, using metacresolas special assistant. The differences between said patent and ourinvention are obvious. The material being dyed, the colors employed andthe assistant found useful are all different in the two cases.

The said patent contains also a reference to copendin application SerialNo. 771,243 (Webb, U. S. P. 2,527,863), which discloses that blends ofacrylonitrile polymers and polyvinyl pyridines may be dyed with acidcolors using metacresol as assistant.

This disclosure, however, is still not relevant to our invention. In thefirst place, a blend of the two polymers mentioned is not the samematerial as a copolymer prepared according to Arnold, U. S. P.2,491,471. In the second place, the copending application seems to beconcerned with dyeing structures at random made from said blend, and isnot concerned with the particular trouble of streaking effects obtainedin the special case of dyeing staple fabric, due to the creasing of thematerial in the process. And finally, the auxiliary agent which we founduseful to solve our special problem is not suggested in said copendingapplication.

We claim as our invention:

1. A process for dyeing modified polyacrylonitrile staple fabric, whichcomprises treating said fabric in rope form with an aqueous solution ofan acid dye in the presence of salicylic acid.

2. A process as in claim 1, the concentration of the salicylic acid inthe dye bath being from 0.5% to 2% by weight.

3. A process for dyeing modified polyacrylonitrile staple fabric, whichcomprises treating said fabric in rope form with an aqueous solution ofan acid dye at a temperature between F. and 200 F., said aqueous dyebath containing salicylic acid in a concentration between 0.5% and 2% byweight.

4. A process as in claim 3, the dyeing being finished in the presence ofsulfuric acid, in quantity not exceeding 0.1 part for each part byweight of fabric being dyed, to assist in exhausting the dye bath.

5. A process as in claim 4, the fabric bein scoured after dyeing, with adetergent and dilute alkali, to remove loosely adhering coloringmaterial and absorbed acid.

PAUL LOUIS MEUNIER. WILLIAM WYGAND, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,491,471 Arnold Dec. 20, 19492,527,863 Webb Oct. 31, 1950 FOREIGN PATENTS Number Country Date 616,385Great Britain Jan. 20, 1949 OTHER REFERENCES American Dyestufi' Reporterfor December 12, 1949, pages P925 to P927.

1. A PROCESS FOR DYEING MODIFIED POLYACRYLONITRILE STAPLE FABRIC, WHICH COMPRISES TREATING SAID FABRIC IN ROPE FORM WITH AN AQUEOUS SOLUTION OF AN ACID DYE IN THE PRESENCE OF SALICYLIC ACID. 